Gas torches are well known. Common fuels used for gas torches include acetylene, propane, butane and other light-weight hydrocarbon fuels. Industrial strength torches have commonly employed acetylene as a fuel and combined the gaseous acetylene with oxygen prior to ignition. This oxygen-acetylene system results in a very hot flame suitable for cutting thick metal. Other hydrocarbon fuels such as butane and propane are more suitable for lower temperature flames adequate for home use.
Recently, air-acetylene torches have been developed which produce a flame lower in temperature than oxygen-acetylene torches but do not require a separate pressurized canister for oxygen. Therefore, the air-acetylene torch systems are more portable than the oxygen-acetylene torch systems. Further, while air-acetylene torches produce a lower temperature flame than oxygen-acetylene torches, they produce a hotter flame than air-butane or air-propane torches. As a result, air-acetylene torch systems are popular with professionals because of their portability and because the flame is hotter than the flame provided by propane or butane.
Hand torches with built-in ignition systems are also known. Prior to the development of built-in ignition systems, the operator of the torch lit the torch with a separate sparking device such as a flint. The sparking device was held out in front of the burn tip after the gas was turned on. This method is not as safe as a built-in method because most built-in methods ignite the gas-air or gas-oxygen mixture inside the burner tube, away from the operator's hands.
Two types of self-ignition devices are currently available. One type offers an ignitor, such as a piezoelectric crystal mounted on the side of the burner tube with an electrode mounted inside the burner tube. A wire connecting the ignitor to the electrode extends down the inside of the burner tube joining the piezoelectric ignitor and the electrode.
This system is flawed because a bridge is required to mount the electrode between the side walls of the burner tube. The bridge and the electrode often interferes with the flow of the flammable fluid mixture in the burner tube thereby interfering with the formation of the flame. The turbulent flow caused by the placement of the bridge and the electrode in the path of the combustible gases can cause the gases to burn inside the tube which is unsafe. The potential for the combustible gases burning inside of the tube is especially great when the torch is operated at low pressures, i.e. 5 psi or less.
The other built-in ignition system currently available involves mounting the ignitor away from the burner tube toward the handle of the torch. A separate conduit is required that extends from the ignitor to the distal end of burner tube near the burn tip. While this system avoids the disadvantages of running a wire down the inside of the burner tube, it requires the separate conduit for the wire connecting the electrode to the ignitor and further requires a bulky mounting at the base of the torch to accommodate the ignitor. Torches known in the art of this type also teach the placement of the electrode in the path of the combustible gases thereby causing the turbulence problem discussed above.
Yet another problem associated with the prior art is the regulation of flame size. Currently, flame size is regulated in gas torches by changing the torch tips. By definition, a torch tip comprises a burn tip, a burner tube and a venturi. The burner tube connects the venturi to the burn tip. The venturi normally connects the torch tip to a handle or gas source. Most manufacturers offer torch tips in a variety of flame sizes and regulate the flame size by lengthening and shortening the burner tube. Short tubes of small diameters result in a smaller, narrower flame. Longer tubes of larger diameters result in a larger, broader flame.
Altering the burner tube size to alter flame size is not cost effective. Specifically, the burner tube is the largest element of a torch tip. By requiring a different burner tube for each different flame size, the kits offering a variety of torch tips for a variety of flame sizes are unnecessarily expensive due to the high cost of manufacture.
The present invention overcomes this problem by regulating the flame size independent of the burner tube size. Specifically, the burner tube size of the present invention remains consistent and the flame size is adjusted by changing the burner tips and the venturis, which are less expensive to manufacture, and consequently less expensive to modify, than the burner tubes.